Peripheral blood lymphocyte phenotyping
The distribution of B and T cells in peripheral blood can be measured by flow cytometry. Lymphocyte subpopulations may change from time to time in response to the dynamic events of immune responses. Therefore, interpretation of results should consider the 'cause' or 'effect' elements; in general, follow-up tests can help define if the abnormal findings are persistent and more likely to be the cause of susceptibility to infections. Importantly, foals present age-dependent developmental changes in the distribution of their lymphocyte subpopulations that should be accounted during interpretation of the results.
Isolated leukocytes from heparinized peripheral blood are treated with different fluorescent reagents that identify cell surface markers; positive cells can be detected by flow cytometry. Therefore, lymphocyte subpopulations (CD4+ T cells; CD8+ T cells; B cells) can be quantified using this technique. In addition, the activation status of these cells may also be assessed with some markers.
Immunological testing in horses:
- serum immunoglobulin concentrations (IgG, IgM, IgA);
- pre- and post-vaccination serum tetanus toxoid or pneumococcal antibody titers;
- peripheral blood lymphocyte phenotyping;
- peripheral blood lymphocyte proliferation;
- peripheral blood neutrophil function (oxidative burst activity).